In the last few years, major progress has been made to elucidate the structure, function, and regulation of P-type plasma membrane H+-and Ca2+-ATPases. Even though a number of regulatory proteins have been identified, many pieces are still lacking in order to understand the complete regulatory mechanisms of these pumps. In plant plasma membrane H+- and Ca2+-ATPases, autoinhibitory domains are situated in the C- and N-terminal domains, respectively. A model for a common mechanism of autoinhibition is discussed.